Three dimensional image projector

ABSTRACT

A method is provided for projecting a three-dimensional image. The method includes providing a first light source that emits first eye images and a second light source that emits second eye images. A polarization of the first light source is orthogonal to a polarization of the second light source. A first eye image of a first color is projected from the first light source. A second eye image of the same first color is projected from the second light source. A first eye image of a second color is projected from the first light source. A second eye image of the same second color is projected from the second light source. A first eye image of a third color is projected from the first light source. A second eye image of a third color is projected from the second light source.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/672,980, filed Nov. 9, 2012, which is a continuation of U.S. patentapplication Ser. No. 13/357,737, filed Jan. 25, 2012, the content ofwhich is hereby incorporated by reference in its entirety.

BACKGROUND

The present invention relates to a stereoscopic three dimensional imageprojector, and more specifically, to a small three dimensional projectorusable with passive glasses.

Three dimensional (3D) movies and pictures have become a popular form ofentertainment due to the increased realism of the images. 3D imagesutilize the human physical trait of binocular vision. Human eyes arespaced about 2 inches (5 centimeters) apart; therefore each eye sees theworld from a slightly different perspective. The brain receives bothimages and has a binocular vision function that correlate the differencebetween what each eye sees to determine distance. The determination ofthe distance provides the three-dimensional effect that a person sees.

To create a binocular image on a two dimensional surface, such as amovie or television screen, the user typically wears glasses. Theglasses alter the way that the user views the images to create thesimulated 3D effect. Typically there are two types of glasses, passiveglasses and active glasses. The type of glasses used will depend on thetype of image projection system being used.

Passive glasses rely upon an optical effect created by using differentlenses for each eye. The projection system emits a sequential series ofimages where subsequent images are slightly offset. The images arearranged such that the user sees the first image through a first lens ofthe glasses (e.g. the right eye) and the second image is seen with theother lens (e.g. the left eye). Since the images are projected quickly,the user does not notice the multiple images, but rather sees a threedimensional effect. Originally, passive glasses used different colorlenses to filter out images; however this limited the use of 3D imageswhen full color images are desired. To alleviate this issue, polarizedlenses were developed where each lens of the glasses allowed thetransmission of different polarized light. The polarized passive lensesallowed for full color 3D images to be transmitted. Passive lenses aremore common with projector type systems, such as movie theaters forexample, where multiple projectors may be used to project the images ona screen.

The development of 3D television systems created a new challenge asthere typically isn't enough room for multiple projectors. Toaccommodate this, active lenses were created. With an active lens, theglasses wirelessly communicate with the projector to synchronize theglasses operation with the images being displayed. With active glasses,the lenses are typically liquid crystal displays that can switch betweentransmitting light and blocking light. In this way, the glasses mayrapidly switch the left and right lenses between clear and opaque. Whilethe glasses are switching, the television is projecting a series ofsequential images. When this switching is synchronized between thetelevision and the glasses, the user experiences a three dimensionaleffect.

Accordingly, while existing three dimensional projectors are suitablefor their intended purpose a need for improvement remains, particularlyin providing a system with a single projector that can project imagesviewable with passive glasses.

BRIEF SUMMARY

According to one embodiment of the invention, a method is providedhaving a first light source and a second light source. A firstpolarizing beam splitter (PBS) is disposed adjacent the first lightsource and a second PBS is located adjacent the second light source. Afirst imaging device is adjacent the first PBS and a second imagingdevice is adjacent the second PBS. Additionally, disposed between thefirst PBS and the second PBS is a third PBS. The first light sourceemits a first light. The first light is reflected from the first PBSonto the first imaging device. The image reflects from the first imagingdevice to the third PBS.

According to another embodiment of the present invention, a method ofprojecting a three dimensional image is provided having a first lightsource with a first polarization and a second light source with a secondorientation wherein the first polarization is orthogonal to the secondpolarization. A first eye image of a first color is projected from thefirst light source. A second eye image of the same first color isprojected from the second light source. A first eye image of a secondcolor is projected from the first light source. A second eye image ofthe same second color is projected from the second light source. A firsteye image of a third color is projected from the first light source. Asecond eye image of a third color is projected from the second lightsource.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification.

The forgoing and other features, and advantages of the invention areapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a schematic view of a three-dimensional image projector inaccordance with an embodiment of the invention;

FIG. 2 is a flow chart for a method of operating a three-dimensionalimage projector in accordance with an embodiment of the invention; and,

FIG. 3 is another flow chart for a method of operating thethree-dimensional image projector in accordance with an embodiment ofthe invention.

DETAILED DESCRIPTION

Contemporary three-dimensional (3D) image projectors that use passiveglasses have typically use two projectors. Previous efforts to use onlya single projector rely upon an active lens within the projector thatswitches between the sequential images. It should be appreciated thatsubstantial costs may be involved in using redundant projectors orhaving a costly active lens. Further, these techniques do not scale wellas users desire comparable performance from smaller and smallerprojector packages.

A second type of projector uses active glasses having a liquid crystaldiode (LCD) lens that coordinates with the projector (typically atelevision). The active glasses alternately block one of the lenses suchthat the user will see sequential images through alternating lenses.While active glasses perform well to create the 3D effect for the user,they also have some less desirable characteristics. The active glassesrequire an energy source such as a battery that needs to be periodicallyrecharged or replaced. If the communication between the television andthe glasses is interrupted, the 3D effect may be lost. Further, due tothe complexity of the system, the active glasses tend to be much morecostly.

With reference now to FIG. 1, a three-dimensional projector 20 is shownfor projecting a three-dimensional (3D) image in accordance with anembodiment of the invention. The projector 20 includes a first lightsource 22 and a second light source 24 arranged to emit light inopposite directions. The direction of light from first light source 22,indicated by arrow 26, is substantially 180 degrees apart from thedirection of the light from second light source 24, as indicated byarrow 28. The first and second light sources 22, 24 may be disposed onopposite sides of centerline 23. In one embodiment, the first and secondlight sources 22, 24 are offset from each other. The first light source22 is spaced a distance D1 from a centerline 23 of the projector and thesecond light source 24 is spaced a distance D2 from the centerline 23.The first and second light sources 22, 24 may be spaced equidistantlyfrom centerline 23 such that distance D1 is equal to distance D2. In theexemplary embodiment, each light source includes three monochromaticlight emitting diodes (LED), a red LED 30, a green LED 32 and a blue LED34. The LED's 30, 32, 34 are arranged to form three sides of a squareand direct light toward the center of the first and second light sources22, 24. Each LED 30, 32, 34 may be coupled to direct light into a lightcollection optic 36.

The light collection optic 36 directs the light from the LED's 30, 32,34 into a dichroic color combiner 38. The dichroic color combiner 38combines light from the LED's to create a desired light color. The lightfrom the first light source 22 exits via an open side 40 and passesthrough a first fly's eye lens 42 and a first pre-polarizer lens 44. Thefirst fly's eye lens 42 consists of an array of lenslets that have theeffect of breaking the transmitted light into many components andprojecting them evenly over the field of view. The result is even,bright illumination without any reduction in light intensity at theperiphery of the projected light. The first pre-polarizer lens 44changes the polarization of the outgoing light to have a desiredpolarization characteristic that is suitable for the imaging devicebeing used. Once the light leaves first the pre-polarization lens 44,the light passes into a first polarizing beam splitter device 54 (PBS).

Similar to the first light source 22, the light from the second lightsource 24 leaves an open side 46 and enters a second fly's eye lens 48and a second pre-polarization lens 50. After being conditioned by theselenses 48, 50, the second light enters a second PBS 58.

A PBS 54, 56, 58 is an optical component that splits incident light raysinto a first (transmitted) polarization component and a second(reflected) polarization component. A first PBS 54 is positionedadjacent to the pre-polarizer lens 44 and a second PBS 58 is locatedadjacent to pre-polarizer lens 50. First and second imaging devices 60,64 are positioned adjacent each of the first and second PBS 54, 58respectively. In one embodiment, the first PBS 54 and the first imagingdevice 60 are arranged on an opposite side of centerline 23 from thesecond PBS 58 and second imaging device 64. The first imaging device 60and the second imaging device 64 may be arranged such that the imagingsurfaces 62, 66 are on opposing sides of centerline 23. In still anotherembodiment, the imaging surfaces are disposed to reflect light in adirection substantially perpendicular to the arrows 26 and 28. In theexemplary embodiment, the imaging devices 60, 64 may be liquid crystalon silicone (LCoS) type devices that have an imaging surface 62, 66adjacent each respective PBS 54, 58. In operation, the light from eitherlighting source 22, 24 reflects off the surface 62, 66 of the respectiveimaging device 60, 64 and back through the respective PBS 54, 58 to amiddle or third PBS 56. For example, if the light was emitted by thefirst light source 22, the first light, reflecting off of the surface 62of the first imaging device 60, will pass through the first PBS 54 tothe third PBS 56 which in turn reflects the first light into aprojection lens assembly 70 and out of the device 20. Similarly, if thelight was emitted by the second light source 24, the second light willreflect off of the surface 66 of second imaging device 64, and passthrough second PBS 58 to third PBS 56. Because the polarization of thesecond light is orthogonal to the polarization of the first light, thethird PBS 56 reflects the light outwards in a direction opposite theprojection lens assembly 70 and towards a mirror 68. The second lightreflects off of minor 68 and reenters third PBS 56. Because the secondlight enters the third PBS 56 from a different angle, the light passesthrough PBS 56 and continues outward towards the projection lensassembly 70 along the same optical path as the first light. Thus thelight from both the first and second light sources 22, 24 exits theprojector 20 and is transmitted along a common optical path. In thepresent embodiment, use of an LCoS imaging device 60, 64 providesadvantages in that the LCoS device inherently polarizes the reflectedlight.

To create a 3D image, the image content for the left and right eye needsto be independently modulated with orthogonal polarizations of light.The light emitted from each light source has a polarization orthogonalto the light emitted from the other light source; consequently, thefirst light source provides all of the image content for a first eye,and the second light source provides all of the image content for theother or second eye. Referring to the flow chart in FIG. 2, theprojector device 20 works by activating the first and second lightsources sequentially such that both the left and right eye images of afirst color are projected before either the left or right eye image of asecond color. In block 90, a light source, such as light source 22,emits a light such that an image for a first eye, such as the left eye,is projected from projector 20. This image will be a first color fromthe plurality of LEDs within the light source, such as red. In block110, another light source, such as light source 24, will similarly emita light of the same color, such that an image for a second eye, forexample the right eye, is projected out of projector 20. Once both lightsources have projected an image of a first color, the first light source22 will then project an image of a second color, such as blue, as inblock 130. In block 132, the second light source will then project animage of the same second color. This pattern repeats in blocks 134 and136 such that the first and second light sources 22, 24 sequentiallyproduce images of a third color from the plurality of LEDs within bothlight sources, such as green. Although the colors need not be projectedin any particular order, conventional systems commonly emit a red lightfirst, a green light second, and lastly a blue light.

In some embodiments, it should be appreciated that the combination oflight sources 22 and 24, polarized beam splitters (PBS) 54, 56, and 58,and LCoS devices 60, 64 provide advantages in reducing the size of theprojector into the category of a pico-projector or micro-projector.These small projectors may be suitable to be used in a portableelectronic device, such as but not limited to a cellular phone, a tabletcomputer, a laptop computer, and a hand-held gaming device for example.Embodiments of the present invention may also be used in non-portabledevices, such as but not limited to a desktop computer or a televisionfor example.

The projector 20 may also include an optional feedback circuit 25. Thefeedback circuit 25 is electrically coupled to communicate with thefirst light source 22, the second light source 24, the first and secondPBS 54, 58 and the first and second imaging devices 60, 64. The feedbackcircuit 25 provides a modulation signal to the light sources 22, 24, tokeep the light sources and LCoS imaging devices synchronized duringoperation. The feedback circuit 25 may additionally include LED driversfor both the first and second light sources 22, 24 to control the orderof the LED colors being used in the images emitted by each source. Thefeedback circuit 25 provides functionality to enable each light source22, 24 to emit the correct color light that corresponds to an imagebeing displayed on the surface 62, 66 of the respective imaging devices.

Referring now to FIG. 3, another method 80 is shown for operating athree dimensional image projector. The method 80 first synchronizes thelight sources in block 84 and creates a first eye image in block 90. Tocreate the first image, a light source, such as first light source 22,emits a first light of a first color LED, for example red, from theplurality of LEDS within the first light source in block 92. In block94, the light is combined by the dichroic color combiner 38 and passesthrough a first fly's eye lens 42 which projects the transmitted lightevenly over the field of view. The light then passes through thepre-polarizer lens 44, as shown in block 96, where the light is given acertain polarization such that it reflects from the first PBS 54. Thelight from the first light source reflects off of the first PBS 54 andonto a first imaging device 60, such as an LCoS imaging device. In block98, the first light reflects off of the first imaging device 60 andthrough the first PBS 54 to a middle or third PBS 56 disposed betweenthe first and second PBS 54, 58. The light reflects out of third PBS 56to a projection lens assembly 70 to project a first eye image of a firstcolor, such as a red image for the left eye. After the first eye imageof a first color is projected, a second eye image of the same firstcolor is then projected, as shown in block 110. To project this secondeye image, in block 112 a light source, such as second light source 24,emits a second light of the same color as the first light emitted byfirst light source 22. The second light similarly is combined by adichroic color combiner 38 and passes through a second fly's eye lens 48which projects the transmitted light evenly over the field of viewcollected by a dichroic minor. In block 116, the second light ispolarized by second pre-polarizer lens 50 such that it reflects from thesecond PBS 58 and onto the second imaging device 64. The light thenreflects off of the surface 66 of the second imaging device 64 in block118, and through the second PBS 58 to a third PBS 56.

Because of the polarization of the second light, which is orthogonal tothe light emitted by the first light source, the second light isreflected from third PBS 56 in a direction opposite the projection lensassembly 70 to a minor 68 as shown in block 120. The second lightreflects off the mirror 68, back through the third PBS 56 and outwardstowards the projection lens assembly 70 along the same optical path asthe first light. In one example, this second light may be the red imagefor the right eye. Once both the first and second light sources haveemitted images using the same first color LED, the first light sourcewill then emit another image for the first eye using a second color LEDfrom the plurality of LEDS within the first light source, as shown inblock 130. Once the second color image from first light source has beenprojected, the second light source will similarly produce an image usingthe same color LED as the prior first light source emission, but adifferent color LED than the previous second light source image. Forexample, if the first set of left and right eye images were red, thenext set of left and right eye images from the first and second lightsources could be either green or blue in color. This cycle continues inblocks 134 and 136 such that both of the images produced by first lightsource and second light source are the remaining color from theplurality of LEDs within the light source. Projection of all three setsof left and right eye images produces a three-dimensional color imagevisible to a viewer wearing passive lenses. The method then loops backto block 90 to continue projecting images from the projector device 20in the color sequence.

Embodiments of the present invention provide for a small, reliablethree-dimensional projector. Embodiments of the present inventionprovide advantages of having multiple light sources that are arranged tohave the same path length for projecting the image. Embodiments provideadvantages in emitting a three-dimensional image usable with passiveglasses.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of onemore other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the preferred embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A method for projecting an image in 3Dcomprising: providing a first light source that emits first eye imagesand a second light source that emits second eye images wherein apolarization of the first light source is orthogonal to a polarizationof the second light source; projecting a first eye image of a firstcolor from the first light source; projecting a second eye image of thefirst color from the second light source; projecting the first eye imageof a second color from the first light source; projecting the second eyeimage of the second color from the second light source; projecting thefirst eye image of a third color from the first light source; and,projecting the second eye image of the third color from the second lightsource.
 2. The method of claim 1 wherein: the first light sourceincludes a plurality of first LEDs, the plurality of first LEDscomprising a first red light emitting diode (LED), a first green LED anda first blue LED; the first eye image of a first color comprises lightemitted from a first LED of the plurality of the first LEDs; the secondlight source includes a plurality of second LEDs, the plurality ofsecond LEDs comprising a red LED, a green LED, and a blue LED; and, thesecond eye image of the first color comprises light emitted from thefirst LED of the plurality of second LEDs such that the first LED of theplurality of first LEDs and the first LED from the plurality of secondLEDs are the same color.